Though Simpson may have been an unlikely bet to be the first celebrity brand to cross the billion-dollar retail mark while other brands have faded, her business partner, Vince Camuto, was unsurprised.

After a short-lived fashion line, Bitten, and a brief stint years later as president and CEO at Halston Heritage, Sarah Jessica Parker has found the right fit in her successful SJP Collection shoe line. Launched in February 2014, Parker teamed with Manolo Blahnik U.S. exec George Malkemus to create the line, which includes designs such as the Carrie, naturally. In November, she took home FN’s Launch of the Year Award. Of the success of SJP Collection, she told FN, “The thing about a launch is that you have to maintain it. That one moment is really exciting, but it’s the long run that we’re looking at.”

L.A.M.B. began as a passion project in Gwen Stefani’s kitchen. This year, the line celebrated two major milestones: its 10th anniversary and its first season back at New York Fashion Week in three years. The singer/designer said she chose to sit out of showing so she could spend time with her three children: Kingston, Zuma and her youngest, Apollo. She also debuted a new collection, Gx by Gwen Stefani, with longtime footwear partner Titan Industries, and told FN, “I feel that I’ve earned the right to be able to do this now, and at the end of the day, an accessory line feels good.”

Admired for her unique personal style, Nicole Richie launched her lifestyle brand, House of Harlow 1960, in spring 2010. The line — a celebrity favorite — has blossomed to include footwear, ready-to-wear, jewelry, eyewear and handbags, and recently added a home fragrance. Of her own sense of style, Richie, who was named 2014 Style Influencer of the Year by FN, said, “[Comfort] leads everything. I’m not the girl who will wear 7-inch heels and be miserable all night.”